[TYPO3] Error: "500 EOF when chunk header expected" when validating page

[Ralf Merz]

Hi list,

does anyone of you have experience with this error message:
"500 EOF when chunk header expected" ?

I get this message when I want to validate my page (doesn´t matter which 
one) on w3c.org using the HTML Validator. When I look at the page on a 
browser, everything is ok.
However, when I want to validate the bakend-login page, it validates on 
w3c.org.
So I guess it is not a problem of TYPO3.

The error-message also appears in "nagios", a monitoring software.
I use TYPO3 4.1.3

The website is running on a "1&1 managed server". The problem occured on 
January, the 5th. Since then I have this error-message and another thing 
which makes problems is that since then the webserver writes 0 byte 
PHP-session fiels in tmp-Folder. Don´t know if this has to do anything 
with each other.

"1&1"-Support told me that there have been no changes on the server. 
Hmmm... who knows?

So, it would be great and would be very thankful if anybody of you has 
nay experience with this behavior or / and this error message.

-- 
--
Greetings
Ralf Merz

Heindl Internet AG
Tübingen , Germany
ralf.merz at heindl.de